We know teens are having sex and opting for oral sex over intercourse because they think it's safer. Now a team of UCSF researchers may be the first to analyze how it makes adolescents feel.

Ninth- and 10th-graders surveyed at two California high schools between 2002 and 2004 revealed mixed emotions that for many included guilt and feeling manipulated.

Girls were more likely than boys to feel bad about themselves afterward and to "feel used." Boys were more likely than girls to say sexual activity made them feel self-confident and popular.

"We tend to focus on the health consequences of having sex, like pregnancy and STDs, but we also need to talk to them about all the emotional consequences," said UCSF pediatrics Professor Bonnie Halpern-Felsher, senior author of the report published this month in the journal Pediatrics.

Of the 618 students her team followed from their freshman year, 44 percent reported having intercourse or oral sex by the end of 10th grade. The report focuses on the surveys from those 275 students and the differing effects of intercourse and oral sex, which researchers said has become more common because teens believe it carries fewer physical and emotional risks.

A majority said they enjoyed sex. The teens who engaged only in oral sex reported fewer problems with sexually transmitted diseases, pregnancy, guilt and their parents -- but less resulting pleasure, self-confidence or intimacy with their partners.

But boys and girls were affected differently. Girls were twice as likely as boys to report feeling bad about themselves, and nearly three times as likely to feel used, according to the UCSF research. Boys were more than twice as likely as girls to report experiencing popularity and self-confidence. (Because the gender differentiation arose in a statistical analysis called a regression, it isn't possible to contrast gender responses with absolute percentages.)

"This report suggests what many teens come to find out on their own: Even if sexual activity seems casual, it often is not," said Bill Albert, deputy director of the nonprofit National Campaign to Prevent Teen Pregnancy in Washington. "A casual hookup on a Friday night might not feel that way a month down the road."

The teens were surveyed, with parental permission, every six months during ninth and 10th grades. Researchers did not disclose what schools the students attended or where in California they lived.

By some counts, teenage oral sex is now more prevalent than intercourse, although teen sexual activity overall is declining and more teens are delaying sexual activity, compared with a decade ago.

More than half of 15- to 19-year-olds surveyed in 2002 had had oral sex, according to the National Survey of Family Growth. And the National Youth Risk Behavior Study has shown a decline in the proportion of high school students having intercourse. Forty-seven percent surveyed in 2005 said they had ever had sex, down from 54 percent in the 1991 survey.

Sex therapist Darcy Luadzers, author of two new advice books for teens about how to navigate the sexual world, said she sees the emotional toll firsthand in her practice. The adults she treats have problems that often date back to regretful teenage experiences, she said. Also, in collecting adolescents' stories for her books "Virgin Sex for Girls" and "Virgin Sex for Guys," she found most of them were regretful about their first experiences.

Luadzers, who has raised five teenagers and lives in South Carolina, said the downsides of teen sex hit home when one of her sons was in middle school and reported that several girls in his class offered him oral sex if he'd become their boyfriend.

According to a 2002 federal survey, teens started having intercourse at age 17 on average. One in 7 girls started by age 15, down from 1 in 5 in 1995, according to the National Survey of Family Growth.

Teens hanging out at the Metreon video arcade and the Westfield San Francisco Centre food court one afternoon this week seemed to bear out the research results when asked whether they wanted to be interviewed about sex: The girls were shy and the boys full of bravado. Two boys, ages 14 and 17, who spoke on condition of anonymity, said they became sexually active when they were 12.

They said it seems like sex is prevalent and casual among students at their schools, San Francisco's Washington and Phillip Burton high schools. And in sexual education classes, they said, teachers talk mostly about biology, rarely about emotions. The girls hanging out didn't want to talk at all about sex.

The UCSF researchers concluded that parents and educators should talk more with their children about all consequences -- physical, social and emotional -- of oral sex as well as intercourse. The authors suggest it might be easier to convince adolescents to delay sex if adults acknowledge the benefits, such as feelings of intimacy, and then suggest other ways to achieve them.

"It gives them tools to make better decisions," Halpern-Felsher said.

Teenage sexual activity

Of 618 California high school students tracked by a UCSF pediatric research team between 2002 and 2004, 44 percent reported having intercourse or oral sex by the end of 10th grade.

The finding was in line with national studies showing that almost half of teens from 15 to 17 years old have had oral sex -- 42 percent of girls and 44 percent of boys.

Even among the two-thirds of teens nationwide ages 15 to 17 who have not had intercourse, 21 percent of boys and 18 percent of girls have had oral sex.

Teens have mixed emotions after oral sex and intercourse: 41 percent of kids in the UCSF survey who had oral sex said they felt bad about themselves, compared with 36 percent who reported feeling bad after intercourse. On the other hand, almost 42 percent of teens who had intercourse told UCSF researchers they felt guilty, compared with 20 percent who said they felt guilty after oral sex.

Sources: "Adolescents' Reported Consequences of Having Oral Sex Versus Vaginal Sex" by Sonya Brady and Bonnie Halpern-Felsher of UCSF, published in the February issue of Pediatrics; 2002 National Survey of Family Growth; and 2005 Youth Risk Behavior Survey by Centers for Disease Control and Prevention.